Enhanced SSD reliability

ABSTRACT

A Solid State Drive (SSD) is disclosed. The SSD may include an interface to receive read and write requests from an application on a host. Storage, including at least one chip, may store data. An SSD controller may process the read and write requests from the application. A configuration module may configure the SSD. Storage may include a reliability table which may include entries specifying configurations of the SSD and reliabilities for those configurations.

RELATED APPLICATION DATA

This application is a continuation of U.S. patent application Ser. No.16/853,731, filed Apr. 20, 2020, which claims the benefit of U.S.Provisional Patent Application Ser. No. 62/948,792, filed Dec. 16, 2019,both of which are incorporated by reference herein for all purposes.

FIELD

The inventive concepts relate generally to storage systems, and moreparticularly to storage systems that storage systems offering variablelevels of reliability.

BACKGROUND

Ideally, storage devices, such as Solid State Drives (SSDs), would beperfect: every bit written could be read without error. But the realworld is not perfect: errors occur occasionally, despite the bestefforts of SSD manufacturers.

To aid consumers, manufacturers may provide estimates of the reliabilityof a device. For example, a manufacturer might report a reliability of99.99% (or its equivalent, an average error rate of 1 bit per 1000 bitswritten and/or read). (In reality, this reliability is relatively low:it would imply at least one error in almost every page written to theSSD. But this reliability level works as an example.)

But this reliability relates to the number of bits written to the SSD orread from the SSD. This reliability may not accurately reflect thereliability of the data from the point of the application. There areother functions performed by the SSD that may impact its truereliability.

A need remains to more accurately determine the reliability of storagesystems and to control the reliability of storage systems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a system including a clients and a server, the serverincluding a Solid State Drive (SSD), according to an embodiment of theinventive concept.

FIG. 2 shows details of the server of FIG. 1 .

FIG. 3 shows details of the SSD of FIG. 1 .

FIG. 4 shows a reliability table for the SSD of FIG. 1 .

FIG. 5 shows an alternative view of the SSD of FIG. 1 .

FIG. 6 shows messages exchanged between an application of FIG. 5 and theSSD of FIG. 1 .

FIG. 7 shows a flowchart of an example procedure for the SSD of FIG. 1to configure itself to provide a desired reliability, according to anembodiment of the inventive concept.

FIG. 8 shows a flowchart of an example procedure for the SSD of FIG. 1to configure itself.

FIGS. 9A-9B show a flowchart of an example procedure for the SSD of FIG.1 to determine a desired reliability.

FIG. 10 shows a flowchart of an example procedure for the SSD of FIG. 1to determine the effective reliability of the SSD of FIG. 1 .

FIGS. 11A-11B show a flowchart of an example procedure for theapplication of FIG. 5 to instruct the SSD of FIG. 1 to provide a desiredreliability, according to an embodiment of the inventive concept.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the inventiveconcept, examples of which are illustrated in the accompanying drawings.In the following detailed description, numerous specific details are setforth to enable a thorough understanding of the inventive concept. Itshould be understood, however, that persons having ordinary skill in theart may practice the inventive concept without these specific details.In other instances, well-known methods, procedures, components,circuits, and networks have not been described in detail so as not tounnecessarily obscure aspects of the embodiments.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first module could be termed asecond module, and, similarly, a second module could be termed a firstmodule, without departing from the scope of the inventive concept.

The terminology used in the description of the inventive concept hereinis for the purpose of describing particular embodiments only and is notintended to be limiting of the inventive concept. As used in thedescription of the inventive concept and the appended claims, thesingular forms “a”, “an”, and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willalso be understood that the term “and/or” as used herein refers to andencompasses any and all possible combinations of one or more of theassociated listed items. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof. The components and featuresof the drawings are not necessarily drawn to scale.

As an example of how the reliability listed by the manufacturer may notaccurately reflect the true reliability of a storage device, considerdata compression. If a Solid State Drive (SSD) compresses the databefore writing the data, then a single bit error in the compressed datamay actually affect multiple bits in the raw data. For example, if thedata is compressed with an effective ratio of 2:1 (that is, the size ofthe data written is ½ the size of the raw data), then a single bit errormay be expected to affect two bits in the raw data, effectively doublethe average error rate. Or in a worst case scenario, the error mayprevent the SSD from being able to successfully decompress the raw data,rendering the entirety of the raw data lost.

Or consider data deduplication. In data deduplication, the SSD attemptsto improve the storage efficiency by identifying chunks of data that arethe same across multiple files (or even entire files that are storedidentically multiple times). Instead of storing multiple copies of thedata, the SSD may store only one copy and reference that copy from thevarious files that include that chunk of data. But if there is an errorin the data that would have been duplicated, that error becomes an errorin every file that uses that data, again magnifying the error rate. Forexample, if the same data is used in three different files, then asingle error in the duplicated data is effectively three errors in threedifferent files.

In addition, different applications may each have different reliabilityrequirements. For example, one application may want there to be no morethan 1 error in 1 MB written by the application, whereas anotherapplication might want there to be no more than 1 error in 1 GB of datawritten by the application. While applications may specify suchreliability rates to help select from among different storage devicesavailable, there is currently no way for a single storage device tosupport multiple different reliability levels.

Depending on the implementation, SSDs may include multiple levels atwhich reliability may be managed. These may include the memory chipsthemselves (where the data is actually stored), which may be flashmemory chips such as NAND flash memory chips, Non-Volatile Memory chips,or other types of memory chips, using an Error Correcting Code (ECC)module (which may detect and/or correct for errors read from the memorychips), and in a RAID/Erasure Coding implementation (where data may bestored across multiple memory chips via multiple channels to provide forsome redundancy).

There are various ways to provide for error detection and correctionusing a Redundant Array of Independent Disks (RAID) or with ErasureCoding. For example, RAID 1, RAID 5, RAID 6, or alternative erasurecoding implementations may support error correction. Each implementationoffers varying degrees of reliability.

ECC modules may also be used, and may implement any desired ECCalgorithms. Example algorithms that may provide for error detectionand/or correction include a basic parity check, Cyclic Redundancy Check(CRC), Hamming Codes, and the like are all well-known schemes forperforming error detection and/or correction. Each implementation offersvarying degrees of reliability.

Finally, NAND flash memory chips may also offer some options with regardto reliability. For example, consider a Single-Level Cell (SLC). An SLCmay store one bit of data. By applying an appropriate voltage to thecell, the SSD may read the bit (that is, applying one voltage to thecell the cell may be determined to store the value “0”, whereas byapplying a different voltage to the cell the cell may be determined tostore the value “1”). Multi-Level Cells (MLCs) store two bits of data,thereby requiring up to four different voltage levels to determine thevalue stored in the cell; Triple-Level Cells (TLCs) store up to threebits of data, thereby requiring up to eight different voltage levels todetermine the value stored in the cell; and Quad-Level Cells (QLCs)store up to four bits, requiring up to 16 different voltage levels todetermine the value stored in the cell.

As the number of bits stored in the cell increases, the width of thevoltage ranges that separate different possible stored values becomessmaller. Thus, it is more likely that a QLC will return an error due toan error from processing the applied voltage than an SLC will returnsuch an error (the same is true for MLCs and TLCs). In addition, cellstends to support fewer writes as the number of bits they storeincreases. Thus, an SLC may support up to 100,000 data writes, whereas aQLC may support up to only 100 data writes (after which errors are morelikely to occur in writing the data). (In addition, because the numberof voltages that must be applied to the cell to determine its valueincreases with the number of bits stored in the cell, it may take longerto read data from a cell from a QLC than from an SLC).

Since there is a relationship between the number of bits stored in acell and the likelihood of an error due to incorrect processing of theinput voltage, it is reasonable to conclude that QLCs are more likely toexperience such an error than the other cell types (or alternatively,that QLCs are the least reliable cell type), with SLCs being the leastlikely to experience such an error (or the more reliable). Of course,unless the NAND flash memory chip offers cells of both types it is notpossible to store data a desired cell type to achieve a particularreliability. But it is possible to use a cell to store fewer bits thanit is capable of storing, thereby increasing its reliability.

Consider the QLC type. If the QLC stores 4 bits of data its reliabilityis as advertised. But if the QLC stores, say, only one bit (leaving theother three bits with default values or “don't care” values), then theQLC is effectively emulating an SLC. Errors that might be introduced dueto voltage processing errors that distinguish among values of the “don'tcare” bits become irrelevant: there are effectively only two inputvoltages that need to be applied to determine the value in the cell.(Embodiments of the inventive concept are not suggesting that the QLCmight be implemented to potentially store and read only one bit, butthat information returned relating to the “don't care” bits may beignored, along with any errors that might relate to that information.Embodiments of the inventive concept are also not suggesting thatstoring only one bit at a time in a QLC might result in the QLCsupporting an increased number of write operations.) Thus, if the QLCwere only storing one bit, the error rate may be reduced, enhancingreliability. The same would be true of any cell type that is used tostore fewer bits than it is designed: thus, the QLC may emulate a TLC,MLC, or an SLC, a TLC may emulate a MLC or an SLC, and a MLC may emulatean SLC, all with an increase in their reliability. (Note that it is notpossible to do the reverse: no cell type may store more than thespecified number of bits of information, even at a reduction in itsreliability.)

It is possible to take a QLC and empirically test it to determine howreliable it is when storing fewer than four bits: the same is true forTLCs and MLCs. This testing would be no different than how QLCs (orother cell types) are tested to determine their normal reliability,except for the amount of data being written to the QLC. Thus, it ispossible to determine, for each cell type, a reliability when storingany number of bits, even when fewer than the maximum number supported bythe cell.

With RAID/Erasure Coding and ECC modules, there are mathematical modelsthat may estimate their reliability, or reliability may be empiricallydetermined by actual use (much like how the reliability of individualcell types may be determined).

It is true that the error correction schemes at the various levels ofthe SSD are not entirely independent of each other. That is, if theerror rate of a RAID implementation and an ECC module were 10⁻¹⁰, andusing a QLC to store only one bit had an error rate 10⁻¹⁰, using allthree in combination would not produce an error rate of 10⁻³⁰ (theproduct of the individual error rates). But the solutions at the variouslevels are at least partially complimentary: using a combination oferror correction schemes at more than one level of the SSD may offer areliability rate that exceeds what may be provided by any individuallevel in isolation.

At the time of manufacture of SSD devices, it is possible to test thereliability of each combination of error correction at the variouslevels, and determine the overall reliability of any individualcombination. Thus, for example, if the NAND flash memory included QLCs,there would be four possible variations (using the QLC to store fourbits, three bits, two bits, or one bit), if the ECC offered threedifferent error correction schemes, and the RAID/Erasure Codingimplementation offered 10 different error correction variations, therewould be a total of 120 different combinations (4×3×10=120). Themanufacturer may test each such combination and determine eachcombination's individual reliability. This information may then bestored in storage within the SSD: for example, within a configurationmodule. The configuration module may also be responsible for selectingthe appropriate combination of error correction at the various levels toachieve a desired reliability.

In some embodiments of the inventive concept, the applications mayspecify the reliability to be applied to their data. For example, someapplications may require the data to be highly reliable, whereas otherapplications may not care as much if the data is lost (such as fortemporary data or data that is easily reconstructed if lost). Given theapplication's specified reliability, the configuration module mayconfigure the SSD to achieve that target reliability for theapplication's data using the reliability rates for the various errorcorrecting combinations. Note that if multiple applications are writingdata to the same SSD, the configuration module may configure the entireSSD to operate at the highest reliability required by any of theapplications, or the configuration module may configure different areasof the SSD to operate at different reliability levels. For example,without changing the RAID or ECC implementation, the SSD may store onlyone bit in QLCs for data requiring a higher reliability and may storefour bits in QLCs for data that tolerates a lower reliability. Note thatembodiments of the inventive concept may support managing reliability atany desired unit of data: page, block, plane, die, chip, or over theentire SSD.

In other embodiments of the inventive concept, the applications maysimply provide the data, without also providing a reliabilityrequirement for the data. In such embodiments of the inventive concept,and more particularly in embodiments of the inventive concept where theSSD may use compression, data deduplication, or any other transactionsthat may have an impact of reliability, the SSD may track what theeffective reliability is for any particular unit of data. Thus, if theapplication's raw data is being compressed, the SSD may track theeffective compression ratio of the data, which may be used to determinea multiplier for the error rate. Or, if the SSD uses data deduplication,the SSD may track how many files are sharing a particular unit of data,which (again) may be used to determine a multiplier for the error rate.Then, to ensure an advertised reliability is achieved, the configurationmodule may use this information, in combination with the reliabilityrates for the various error correcting combinations, to select anappropriate combination that provides the advertised reliability(factoring in how errors are multiplied based on the SSD' s operations).

Note that reliability is not the only variable to consider in selectingan error correcting combination to achieve a target reliability(although it may be the primary variable). If reliability alone were theonly consideration, then the SSD could simply be configured to use theerror correcting combination that offered the highest reliability and bedone with it: no higher reliability could be achieved. But the variouserror correcting combinations also have other implications. These otherimplications include space overhead and performance. For example, if aQLC is used to store only one bit of information, the QLC is operatingat a higher reliability, but is only ¼ as efficient in terms of storage(since the QLC could store as many as four bits). Performance is also aconsideration: Different error correcting combinations may require moretime to process the data, which may affect the latency of the SSD.

Thus, factoring in other considerations, the configuration module mayselect which error correcting combination to use to configure the SSDthat offers at the target reliability rate. For example, if spaceoverhead is considered an important factor, an error correctingcombination that lets the QLC store four bits of data (relying more onthe ECC module or the RAID/Erasure coding) may be preferred over anerror correcting combination that stores only one bit in the QLC.Alternatively, if performance is a bigger issue than space overhead, anerror correcting combination that relies less on the ECC module and/orthe RAID/Erasure Coding to correct for the data may be favored, even ifit means that the QLC stores only one bit of data.

FIG. 1 shows a system including a clients and a server, the serverincluding a Solid State Drive (SSD), according to an embodiment of theinventive concept. In FIG. 1 , clients 105-1 and 105-2 are showncommunicating with server 110 over network 115. Clients 105-1 and 105-2and server 110 may be in a client-server relationship: clients 105-1 and105-2 may issue commands and sever 110 may execute those commands.Alternatively, server 110 may be a computer being used directly by anend user, avoiding the involvement of clients 105-1 and 105-2.

Network 115 may be any variety or varieties of network. For example,network 115 may include a Local Area Network (LAN), a Wide Area Network(WAN), a Metropolitan Area Network (MAN), or a global network such asthe Internet, among other possibilities. Data may be sent across network115 directly, or it may be protected: for example, using encryption or aVirtual Private Network (VPN). Network 115 may include wired or wirelessconnections. In addition, network 115 may include any desiredcombinations of these alternatives. For example, clients 105-1 and 105-2might be connected via a wireless connection to a LAN that in turnconnects via a wired connection to the Internet, which in turn connectsto another LAN to which server 110 is connected. The connections betweenclients 105-1 and 105-2 and server 110, may vary: the connections do nothave to be the same in all situations.

Server 110 may include processor 120, memory 125, and Solid State Drive(SSD) 130. Processor 120 may include a software stack, including theoperating system, applications, storage software (such as a filesystem), and controller software to manage devices attached to server110 (such as memory 120 and SSD 130). Processor 120 may be any varietyof processor: for example, an Intel Xeon, Celeron, Itanium, or Atomprocessor, an AMD Opteron processor, an ARM processor, etc. While FIG. 1shows a single processor 120, server 110 may include any number ofprocessors, each of which may be single core or multi-core processors,and may be mixed in any desired combination.

Memory 120 may be conventional memory used in server 110. Memory 120 maybe any variety of memory, such as flash memory, Dynamic Random AccessMemory (DRAM), Static Random Access Memory (SRAM), Persistent RandomAccess Memory, Ferroelectric Random Access Memory (FRAM), orNon-Volatile Random Access Memory (NVRAM), such as MagnetoresistiveRandom Access Memory (MRAM) etc. Memory 120 may be a volatile memory ora non-volatile memory. Memory 120 may also be any desired combination ofdifferent memory types. Memory 120 may be managed by a memory controller(not shown in FIG. 1 ), which may be a separate component in server 110with a driver that is part of the software stack. Memory 120 may be usedto store data that may be termed “short-term”: that is, data notexpected to be stored for extended periods of time. Examples ofshort-term data may include temporary files, data being used locally byapplications (which may have been copied from other storage locations),and the like.

Processor 120 and memory 120 may also support an operating system underwhich various applications may be running. These applications may issuerequests to read data from or write data to either memory 120 or SSD130. Whereas memory 120 may be used to store data that may be termed“short-term”, SSD 130 may be a storage devices used to store data thatis considered “long-term”: that is, data expected to be stored forextended periods of time. SSD 130 may be accessed using controllersoftware in the software stack running on processor 120. While FIG. 1shows only one SSD 130, embodiments of the inventive concept may includestorage devices of any type and connecting via any desired connection.Thus, SSD 130 may be replaced with Serial AT Attachment (SATA) hard diskdrives, Ethernet SSDs, or storage devices of any other types. Further,embodiments of the inventive concept may include any number (zero ormore) of storage devices, and each storage device may be of any desiredtype: thus, multiple different types of storage devices may be mixed inserver 110.

FIG. 2 shows details of server 110 of FIG. 1 . In FIG. 2 , typically,server 110 may include one or more processors 120, which may includememory controllers 205 and clocks 210, which may be used to coordinatethe operations of the components of the machine. Processors 120 may alsobe coupled to memories 125, which may include random access memory(RAM), read-only memory (ROM), or other state preserving media, asexamples. Processors 120 may also be coupled to storage devices 130, andto network connector 215, which may be, for example, an Ethernetconnector or a wireless connector. Processors 120 may also be connectedto buses 220, to which may be attached user interfaces 225 andInput/Output interface ports that may be managed using Input/Outputengines 230, among other components.

FIG. 3 shows details of SSD 130 of FIG. 1 . In FIG. 3 , SSD 130 mayinclude host interface logic (HIL) 305, SSD controller 310, and variousmemory chips 315-1 through 315-8 (also termed “memory storage”), whichmay be organized into various channels 320-1 through 320-4. Hostinterface logic 305 may manage communications between SSD 130 and othercomponents (such as processor 120 of FIG. 1 or other SSDs). Thesecommunications may include read requests to read data from SSD 130 andwrite requests to write data to SSD 130. Host interface logic 305 maymanage an interface across only a single port, or it may manageinterfaces across multiple ports. Alternatively, SSD 130 may includemultiple ports, each of which may have a separate host interface logic305 to manage interfaces across that port. Embodiments of the inventiveconcept may also mix the possibilities (for example, an SSD with threeports might have one host interface logic to manage one port and asecond host interface logic to manage the other two ports).

SSD controller 310 may manage the read and write operations, along withgarbage collection and other operations, on memory chips 315-1 through315-8 using a memory controller (not shown in FIG. 3 ). Memory chips315-1 through 315-8 may be any variety of memory chips, such as NANDflash memory chips or other Non-Volatile Memory chips, althoughembodiments of the inventive concept may extend to other storage systemssuch as Non-Volatile RAM (NVRAM).

SSD controller 310 may include translation layer 325, error correctingcode module 330, RAID/erasure coding module 335, configuration module340, and reliability table storage 345. Translation layer 325 may managea mapping from logical block addresses (LBAs) used by applicationsrunning on processor 120 of FIG. 1 to physical block addresses (PBAs)where data is actually stored on SSD 130. By using translation layer 325(in some embodiments of the inventive concept, translation layer 325 maybe termed flash translation layer 325), SSD 130 may move data around onmemory chips 315-1 through 315-8 without having to keep the applicationabreast of where the data currently resides (this may happen, forexample, when the application requests that the data be overwritten withnew values (SSDs generally do not support overwriting data in place, andtherefore store the new data in a new location) or when a block thatcontains some valid data is subject to garbage collection). Translationlayer 325 may be implemented as a table stored in some (preferably)non-volatile storage somewhere within SSD 130.

Error correcting code (ECC) module 330 may apply error correcting codesto data to be written to memory chips 315-1 through 315-8. In someembodiments of the inventive concept, ECC module 330 may be applied tothe data regardless of which memory chip 315-1 through 315-8 will storethe data; in other embodiments each channel 320-1 through 320-4 (or eachmemory chip 315-1 through 315-8) may have its own ECC module 330. ECCmodule 330 may implement any desired error correcting algorithm, and maytherefore support detection and/or correction of any number of errors(depending on the implemented algorithm). Example algorithms that may beused by ECC module 330 include such as a parity codes, Cyclic RedundancyCheck (CRC) codes, or Hamming codes. ECC module 330 may be implementedusing a general purpose processor executing appropriate instructions, orusing a Field Programmable Gate Array (FPGA), Application-SpecificIntegrated Circuit (ASIC), a Graphics Processing Unit (GPU), or anyother desired implementation.

RAID/Erasure Coding module 335 may implement any desired RAID or erasurecoding scheme to store data on memory chips 315-1 through 315-8. (Sincea Redundant Array of Independent Disks, or RAID, describes a specificset of implementations of erasure coding, RAID/Erasure Coding module 335may be more generally described as an Erasure Coding module with noreduction in functionality.) In general, RAID/Erasure Coding module 335may take data to be written on SSD 130, divide that data into variousunits, and store those units on different memory chips 315-1 through315-8. To introduce redundancy, the same data may be stored on multiplememory chips 315-1 through 315-8, or error correcting information (suchas a parity codes, CRC codes, or Hamming codes) may be used. In thismanner, errors may be detected and corrected. (Note that the same basicapproaches may be used in both RAID/Erasure Coding module 335 and ECCmodule 330, but at different scales: the solutions therefore maycomplement each other.) Erasure Coding module 335 may be implementedusing a general purpose processor executing appropriate instructions, orusing an FPGA, an ASIC, a GPU, or any other desired implementation.

Configuration module 340 may be used to program what techniques are tobe used to improve reliability. While one might wonder how differentreliability techniques could be used, the answer is simple. ECC module330 and RAID/Erasure Coding module 335 might offer support for differenterror correcting techniques, each with (potentially) differentreliability rates. Configuration module 340 may be used to instruct ECCmodule 330 and/or RAID/Erasure Coding module 335 as to which errorcorrecting technique may be used at a given time.

But this answer leads to a follow-up question: if there are differenterror correcting techniques that offer varying degrees of reliability,why not always use the most reliable approach? The answer is that thedifferent techniques may have other implications for the operation ofSSD 130, which may offset the benefit of the greater reliability. Forexample, consider the possibility that the same data might be stored ineach of memory chips 315-1 through 315-8. This approach introduceseight-fold replication of the data, and the failure of a single memorychip would not lead to the loss of the data. The downside of thisapproach is that since the same data is stored eight times, the totalavailable storage of SSD 130 is no greater than that of a single memorychip. Put in other ways, the total usable storage offered by SSD 130would be only one eighth of the actual storage offered by SSD 130, oralternatively that 87.5% of the available storage is reserved forredundant copies of data. If the data is so sensitive that eight-foldreplication is necessary, this price might be acceptable; but for mostusers such redundancy is overkill and the reduction in usable storageunacceptable.

Thus, configuration module 340 may be used to instruct (or program, orconfigure: whatever term may be preferred) ECC module 330 andRAID/Erasure Coding module 335 to use specific techniques from thoseoffered by ECC module 330 and RAID/Erasure Coding module 335.

Aside from ECC module 330 and RAID/Erasure Coding module 335, there areother components that may be configured by configuration module 340:specifically memory chips 315-1 through 315-8. Different memory chipsmay offer different ways to store data, which may affect the reliabilityof the memory chips. To understand this fact, it is important tounderstand the different types of memory storage.

Memory manages data at varying levels of granularity, depending on whatis happening. For example, the basic unit of access to read and writedata is the page (which may be of any desired size: for example, 4 KB ofdata). Pages may be written if free. But pages may not be overwrittenwhen new data replaces old data: in that situation the original page maybe marked as invalid and the new data written to a new page. Pages areorganized into groups called blocks: for example, a block might have 64or 128 pages. The block (or the superblock, which is a group of blocks)is typically the unit for erasing data (which returns pages to the freestate to be written anew). Thus, if there is any valid data in a blockthat has been selected for erasure, the valid data should be copied outof the block before the block is erased (lest the valid data be lostwhen the block is erased).

But even at finer levels, there are variations on data storage.Individual units, called cells, store data at finer granularity than thepage. (Individual cells may not be directly accessible: the entire pagemay be read or written as a unit.) Each cell is designed to respond whenvarying voltages are applied: these different responses may be used toread (or write) the value to a cell.

In the simplest form, a cell has a single trigger voltage (which may bethought of as a point of demarcation) where its response changes. Thatis, apply a voltage below that trigger voltage and the response will bedifferent from applying a voltage above that trigger voltage. Thus, forexample, if an input voltage might vary anywhere from 0V to 5V, 2.5Vmight be the point at which the cell may start to respond. (How the cellresponds may depend on the value stored in the cell. For example, if thecell represents a binary value of 0, the cell may output one voltage,whereas if the cell represents a binary value of 1, the cell may outputanother voltage.) Cells that store only a single bit are sometimesreferred to as Single Level Cells (SLCs).

Multi-Level Cells (MLC) refer to cells that store more than one bit.While “multi” could be understood to mean “two or more”, in practiceMLCs typically may store two bits, while Triple Level Cells (TLCs) maystore three bits, Quad-Level Cells (QLCs) may store four bits, and soon. Because MLCs (and all other types of cells that store more than onebit) store multiple bits, MLCs have multiple trigger voltages. Forexample, if an input voltage might vary anywhere from 0V to 5V, an MLCmight have trigger voltages at 1V, 2V, 3V, and 4V. Depending on thetrigger voltage, the flash memory chip may determine the actual valuestored in the cell. Thus, for example, if the trigger voltage is 1V, thecell may store the value 00; if the trigger voltage is 2V, the cell maystore the value 01; if the trigger voltage is 3V, the cell may store thevalue 10; and if the trigger voltage is 4V, the cell may store the value11.

The various cell types have different advantages/disadvantages.Obviously, the ability to store more than one bit of information percell means that fewer cells are needed to store the same amount of data.Thus, if data is stored in SLCs, more SLCs are needed than MLCs, TLCs,or QLCs would be needed to store the same amount of data. Whileindividual cells that store more bits tend to be more expensive thancells that store fewer bits, the increased cost may be offset by needingfewer such cells. Thus, to store the same amount of data, in generalQLCs may be cheaper than TLCs, which may be cheaper than MLCs, which maybe cheaper than SLCs.

But there are other factors that may offset cost. First, since the SSDhas to test the cells against multiple different voltages to determinethe value stored in a cell, the more such tests that need to beperformed may slow down the performance of the cell. For example,consider a QLC. Since a QLC stores four bits of data, the QLC may takeany of 16 possible values. Thus, to read the QLC may require testing theQLC against 16 possible trigger voltages, which takes longer thantesting a cell against two trigger voltages. Thus, QLCs may be slower toread than TLCs, which may be slower to read than MLCs, which may beslower than SLCs. In addition, the more bits the cell may store, thefewer the number of program/erase cycles in the cell's lifetime. Forexample, SLCs may guarantee 100,000 program/erase operations before acell may fail, whereas that number may drop to 10,000 for MLCs, 1,000for TLCs, and 100 for QLCs. Therefore, different types of cells may bebetter utilized for different storage profiles: QLCs may be better usedto store data that almost never changes, whereas SLCs may be used fordata that changes with relative frequency.

A final disadvantage of cell types relates back to the number of triggervoltages needed for cells that store higher densities of data. Thegreater the number of trigger voltages, the more closely spaced thosetrigger voltages may be to each other. But the closer the triggervoltages are to each other, the more vulnerable the cell is to potentialerror. For example, consider a QLC. Since a QLC may store four bits ofdata, there are 16 possible values in the QLC. To distinguish among 16possible values may require 16 trigger voltages, which means the gapbetween trigger voltages may be little more than 0.25V. It would notrequire a tremendous dip or surge in voltage for the cell to think it isresponding to a different voltage than that actually intended, whichmeans that the QLC might respond incorrectly to an attempt to read thecell. (This same analysis is applicable to MLC and TLC cell types aswell, although the margins of error are larger since there are fewertrigger voltages to consider.)

So, returning to the question of reliability, QLCs may store higher datadensities, but at the cost of reduced margins of error. But just becausea QLC (or any type of cell that stores two or more bits of data) maystore multiple bits does not mean that the QLC must store multiple bits.Such a QLC might be used to store fewer than four bits of data, with anyvalues assigned to the other bits in the QLC being ignored on readoperations. By storing fewer bits in the QLC, the effective number oftrigger voltages is reduced, which may widen the margins of error. (Notethat the QLC may still be hardwired to test against all 16 triggervoltages; only the possibility of an error is reduced, not the timerequired to access the cell.)

For example, assume that a QLC were used to store only one bit of data.This value (be it 0 or 1) may be stored in any of the four bits of theQLC, with the other bits effectively ignored by the SSD (that is, thosebits may be assigned any arbitrary values at the time the cell iswritten, and any values read from those bits may be ignored and only thebit of interest returned). Since the QLC now effectively has only onetrigger voltage, the likelihood that the cell is written or readincorrectly (for example, due to a voltage fluctuation) is reduced.

Thus, it may also be possible to influence the reliability of the SSD bychanging the operational behavior of even flash memory chips 315-1through 315-8. But there are a couple of caveats to consider. First,whether the reliability of the SSD may be influenced by changing theoperational behavior of flash memory chips 315-1 through 315-8 dependson the type of cells used in flash memory chips 315-1 through 315-8. Thehigher the data density of the cells, the more options there are toinfluence the reliability of the SSD. SLCs, for example, only store onebit of data, so the reliability of an SSD that uses only SLCs may not beimproved by changing the operational behavior of the SLCs.

Further, the improvement described above operates only in one direction.A cell that is capable of storing a higher density of data may be usedto store lower density data by ignoring some of the bits in the cell.But it is not possible to decrease the reliability of the SSD byattempting to store more bits in the cell than the cell may store. Forexample, since an SLC may only store one bit of data, it is not possible(regardless of the reduction in reliability that might be tolerated) tostore two bits in an SLC. (Of course, a cell that stores fewer bits thanit is capable of storing may have its data density increased, providedthe increase does not exceed the capabilities of the cell. Thus, forexample, a QLC that is capable of storing four bits but is currentlystoring only two bits may have its data density increased to three bitsor four bits, but not to five bits.)

Second, as with using flash memory chips 315-1 through 315-8 to allstore the same data, storing fewer bits in a cell than it is capable ofstoring may result in less usable storage in the SSD. For example,consider an SSD that uses QLC cells and has a total available storagecapacity of 1 TB. If the QLCs are used to store only one bit per cell,then the SSD has an effective capacity of only 256 GB (25% of the totalavailable storage capacity): the remaining 768 GB of storage are “lost”in the unused bits of the QLCs.

On the other hand, different flash memory chips may be configured toachieve different overall reliabilities. Thus, for example, assume thatflash memory chips 315-1 through 315-8 all use QLC cells. Flash memorychip 315-1 may be configured to store only one bit in each cell, therebyoffering increased reliability at the cost of reduced available storage.Flash memory chip 315-2, on the other hand, may be configured to storefour bits in each cell, thereby offering maximum available storage atthe cost of lower reliability.

Configuration module 340 may be implemented using a general purposeprocessor executing appropriate instructions, or using an FPGA, an ASIC,a GPU, or any other desired implementation. In FIG. 3 , ECC module 330,RAID/Erasure Coding module 335, and configuration module 340 are shownas different components. Because these components may be manufacturedseparately and installed in SSD 130, they may be implemented as separatecomponents. In addition, these components may actually reside inphysically different locations. For example, as discussed above andfurther below with reference to FIG. 5 , ECC module 330 may apply toindividual channels (but to multiple memory chips), whereas RAID/ErasureCoding module 335 may apply across multiple channels. In suchconfigurations, it is unlikely that any of ECC module 330, RAID/ErasureCoding module 335, and configuration module 340 may be implemented usingcommon hardware. But in some embodiments of the inventive concept it maybe possible for any or all of these components to be implemented usingcommon hardware.

The above discussion focuses on what configuration module 340 may do toconfigure memory chips 315-1 through 315-8, ECC module 330, andRAID/Erasure Coding module 335, but no explanation has yet been given asto what would trigger configuration module 340 to perform suchoperations. FIGS. 5-6 below discuss what might trigger configurationmodule 340 to perform its operations.

Finally, to support configuration module 340, SSD 130 may includereliability table storage 345. Reliability table storage 345 may store areliability table. This reliability table may provide information aboutthe reliability offered by various combinations of schemes used bymemory chips 315-1 through 315-8, ECC module 330, and RAID/ErasureCoding module 335.

FIG. 4 shows a reliability table for SSD 130 of FIG. 1 . In FIG. 4 ,reliability table 405 is shown. Reliability table 405 includes variouscolumns, such as storage schemes 410, ECC schemes 415, and erasurecoding schemes 420. Collectively, storage schemes 410, ECC schemes 415,and erasure coding schemes 420 form configurations 425: that is, for agiven entry in reliability table 405, storage schemes 410, ECC schemes415, and erasure coding schemes 420 specify how memory chips 315-1through 315-8 of FIG. 3 , ECC module 330 of FIG. 3 , and RAID/ErasureCoding module 335 of FIG. 3 may be configured. Other columns may includereliability 420 (which may specify the overall reliability of a givenconfiguration), space overhead 430 (which may specify any spacelimitations incurred by using the particular configuration) andperformance 435 (which may specify any performance limitations incurredby using the particular configuration). If reliability alone is thedriving consideration in how to configure SSD 130 of FIG. 1 , then spaceoverhead 430 and performance 435 may be omitted from reliability table405.

Reliability table 405 may include entries for each possibleconfiguration of SSD 130 of FIG. 1 . For example, FIG. 4 showsreliability table as including six entries 440, 445, 450, 455, 460, and465. Each entry represents a different possible configuration of SSD 130of FIG. 1 . Thus, for example, entry 440 identifies the reliability fora configuration that uses Storage scheme 1 for memory chips 315-1through 315-8 of FIG. 3 , ECC scheme 1 for ECC module 330 of FIG. 3 ,and Erasure Coding scheme 1 for RAID/Erasure Coding module 335 of FIG. 3. For this configuration, the overall reliability is 1 error in 10¹²bits written or read. This configuration also imposes no space overheador performance overhead (entry 440 may represent, for example, thedefault configuration of SSD 130 of FIG. 1 , in which case thereliability rate for entry 440 may be the advertised reliability ratefor SSD 130 of FIG. 1 ). In contrast, entry 445 represents aconfiguration that uses Storage scheme 2 for memory chips 315-1 through315-8 of FIG. 3 , ECC scheme 1 for ECC module 330 of FIG. 3 , andErasure Coding scheme 1 for RAID/Erasure Coding module 335 of FIG. 3 .This configuration has a reliability rate of 1 error in 10¹⁴ bitswritten or read, but imposes a 50% reduction in the available storagecapacity of SSD 130 of FIG. 1 (but no performance overhead). Forexample, entry 445 may represent a configuration where data is writtento two different memory chips for redundancy, which improves the overallreliability of SSD 130 but at the cost of reducing the amount ofavailable storage.

Entries 450 and 455 are similar to entries 440 and 445, but with ECCmodule 330 of FIG. 3 using ECC scheme 2. As may be seen, theseconfigurations have reliability rates of 1 error in 10¹⁶ and 10¹⁸ bits,respectively: a 10⁴ improvement over the configurations shown in entries440 and 445. But because ECC scheme 2 may require more computationalresources than ECC scheme 1, the configurations represented by entries450 and 455 may impose a performance hit of 25% (that is, SSD 130 ofFIG. 1 may require 25% more time to process a read and/or write requestusing the configurations represented by entries 450 and 455 than theconfigurations represented by entries 440 and 445).

Entries 460 and 465 are similar to entries 440 and 445, but withRAID/Erasure Coding module 335 of FIG. 3 using Erasure Coding scheme 2.As may be seen, these configurations have reliability rates of 1 errorin 10¹⁴ and 10¹⁷ bits, respectively, which represent 10-100 timesgreater reliability. But because Erasure Coding scheme 2 may requiremore computational resources than Erasure Coding scheme 1, theconfigurations represented by entries 460 and 465 may impose aperformance hit of 10% (that is, SSD 130 of FIG. 1 may require 10% moretime to process a read and/or write request using the configurationsrepresented by entries 460 and 465 than the configurations representedby entries 440 and 445).

Note that the improvement offered by Erasure Coding scheme 2 alone isnot the same for both of configurations 460 and 465. Entries 460 and 465represent the fact that while combining different schemes for differentcomponents of SSD 130 of FIG. 1 may offer improvements relative to onlyone component providing any reliability, neither are the benefits ofcombining schemes for different components entirely orthogonal. Putanother way, using reliability options of multiple components may besuperior to using a reliability option of a single component, but thereliability rates of the two components may not simply be multipliedtogether to determine the reliability rate when both components are usedto enhance reliability. Thus, for example, even if there are particularschemes that offer error rates of 1 error 10¹⁰ bits read or written inmemory chips 315-1 through 315-8 of FIG. 3 , ECC module 330 of FIG. 3 ,and RAID/Erasure Coding module 335 of FIG. 3 , using all three schemestogether does not necessarily result in an error rate of 1 bit in 10³⁰bits read or written.

So if the reliability rate of a combination of schemes may not becalculated as the product of the reliability rates of the separateschemes, how might the reliability rate of a particular configuration bedetermined for entry in reliability table 405? The answer is for themanufacturer of SSD 130 of FIG. 1 to test every possible configurationseparately. That is, various SSDs may be configured to use each possiblecombination of configurations. These SSDs may then be tested to see whattheir respective error rates (and space overhead, and performanceoverhead) are. This information may then be stored in reliability table405 for all SSDs manufactured according to the same specifications.

In addition, while FIG. 4 shows only combinations of different schemesfor reliability using each of memory chips 315-1 through 315-8 of FIG. 3, ECC module 330 of FIG. 3 , and RAID/Erasure Coding module 335 of FIG.3 , reliability table 405 may also be used to show the reliability rates(and space and performance overheads, if desired) of individual schemes.For example, reliability table 405 may include entries for storageschemes 1 and 2 for memory chips 315-1 through 315-8 of FIG. 3 , with noassociated schemes for ECC module 330 of FIG. 3 or RAID/Erasure Codingmodule 335 of FIG. 3 : in that case, those entries may represent thereliability rate of using storage schemes 1 and 2, respectively (withoutadding any reliability enhancement from ECC module 330 of FIG. 3 orRAID/Erasure Coding module 335 of FIG. 3 ). Similarly, reliability table405 may include entries for just ECC schemes 1 and 2, and/or for ErasureCoding schemes 1 and 2.

Reliability table 405 may be searched along multiple axes. For example,reliability table 405 may be used to determine the reliability (andother consequences, such as space overhead and/or performance) of aparticular configuration. Reliability table 405 may also be used todetermine a configuration that supports a particular reliability. Thatis, given a particular desired reliability rate, reliability table 405may be searched to find a particular configuration to offers thatreliability rate (or a superior reliability rate).

If multiple configurations may offer the desired reliability rate (or asuperior reliability rate), configuration module 340 of FIG. 3 mayselect among the options using any desired approach. For example,configuration module 340 of FIG. 3 might select the configuration thatoffers the highest reliability rate, or the lowest reliability rate thatmeets or exceeds the desired reliability rate. Or, configuration module340 of FIG. 3 may use the space overhead and/or the performanceconsequences of the configuration (if included in reliability table 405)to select the configuration that offers a sufficient reliability ratewith the fewest other consequences. Configuration module 340 of FIG. 3may also use any other desired technique to select from among multipleconfigurations that offer sufficient reliability.

To assist in identifying a particular combination in reliability table405, reliability table 405 may also include identifier 475. Identifier475 may be a unique identifier assigned to each entry in reliabilitytable 405. Thus, for example, entry 440 may by assigned identifier “1”,entry 445 may be assigned identifier “2”, and so on. Note that there isno requirement that identifiers 475 be numerical or sequential. Forexample, identifiers 475 may be random strings, or hashes of informationshown in the entry, or any other desired identifiers. The only helpfulelement is that identifiers 475 may be unique, so that a unique entry inreliability table 405 may be located using a given identifier.

Returning to FIG. 3 , while FIG. 3 shows SSD 130 as including eightmemory chips 315-1 through 315-8 organized into four channels 320-1through 320-4, embodiments of the inventive concept may support anynumber of memory chips organized into any number of channels. Similarly,while FIG. 3 shows the structure of an SSD, other storage devices (forexample, hard disk drives) may be implemented using a differentstructure, but with similar potential benefits.

FIG. 5 shows an alternative view of SSD 130 of FIG. 1 . In FIG. 5 , SSD130 is shown as including RAID/Erasure Coding module 335, ECC modules330-1, 330-2, and 330-3, which may operate along channels 320-1, 320-2,and 320-3, respectively, which include memory chips 315-1, 315-2, and315-5. Thus, data may be organized using RAID or Erasure Coding to bestored on multiple memory chips, each of which may be on different (orthe same) channels.

Data may be received from applications 505-1 and 505-2 (although theremay be any number (one or more) of applications). Each application mayhave its own desired reliability 510-1 and 510-2. Each applications'desired reliability represents the reliability rate that thatapplication desires. Note that desire reliabilities 510-1 and 510-2 donot have to agree: each application may expect a different reliabilityrate.

Each application 505-1 and 505-2 may have its own associated namespace515-1 and 515-2, respectively. Namespaces 515-1 and 515-2 provide waysto organize data coming in from each application so that they may beeasily identified and/or grouped together. The use of namespaces 515-1and 515-2 is optional.

FIG. 5 refers to the concepts of data deduplication and compression.Data deduplication references the idea that there may be multiple copiesof a particular data stored on SSD 130. Rather than storing the multiplecopies, a single copy may be stored and the other copies reference thestored copy. In so doing, the amount of space that would be used instoring the multiple files is reduced.

For example, consider an image file, such as a photograph. It is notunusual for the same photograph to be stored multiple times, perhapswith different file names (as it is easy to forget that the photographwas previously stored using a different name). But it is simple enoughfor the host machine or SSD 130 to recognize that a particular file is aduplicate of a previously stored file (assuming SSD 130 includes someprocessing capability to identify duplicate files). There is no need tostore the same photograph multiple times: a single copy will suffice(with references from the other folders where the duplicates werestored).

As an example of how data duplication may be identified, a cryptographichash may be generated of each file. If the cryptographic hashes of twofiles are the same, there is a possibility (perhaps a strongpossibility) that the two files contain the same data. Thus, determiningif a new file is duplicate of a file already stored on SSD 130 merelyrequires generating the cryptographic hash of the new file, comparingthat cryptographic hash against cryptographic hashes of other files(perhaps using a hash table), and if a match is found then performing a(detailed) comparison of the data in the matched files.

Note that data deduplication may operate on any desired unit of data.While files are a common unit for data deduplication, other units may beblocks or pages (units of data within SSD 130). Still other units ofdata may also be used.

Compression, on the other hand, refers to techniques by which data maybe stored in a manner that takes up less space than the raw data.Consider, for example, the number 10¹⁰⁰ (commonly referred to a googol).To store this number as a raw value would require approximately 2³⁰⁰bits, or 2³⁸ bytes (assuming a computer was designed to store an integerthis large). On the other hand, this number could also be represented asa “1” followed by 100 “0”s. Using an encoding scheme such as Run LengthEncoding, this value could be represented using four bytes: 1, 1, 100, 0(that is, one copy of the value “1”, and 100 copies of the value “0”).Since four bytes is considerably less than 2³⁸ bytes, the space savingsof using encoding for this value is significant to say the least. (While“compression” as a term typically refers to algorithms that encode datausing structures such as Huffman codes, in this context “compression”refers to any technique that may be used to reduce the amount of spacetaken up by data, and thus may include techniques commonly referred tousing terms such as “encoding”.)

While data deduplication and compression have their benefits, in thatthey reduce the “footprint” data may take on a storage device, they havepotential disadvantages as well, particularly when discussing errors.Assume, for example, that a particular file as stored on SSD 130actually contains data for five different files (one original and fourduplicates). Since the four duplicates point to the same data as theoriginal file, if there is a single bit error anywhere in the storedfile, then that error would be read whenever any of the file differentfiles is accessed. Thus, a single bit error for the data stored on SSD130 would actually be better understood to be five bit errors: one forthe same bit error in the original file and each duplicate. In otherwords, data deduplication has magnified the error rate of SSD 130 by thenumber of referenced copies of the file.

Similarly, compression may affect what the true error rate is. Consideragain the example of how 10¹⁰⁰ may be stored using Run Length Encoding.If the value “0” were replaced with “1” (a single bit error), that errorwould be magnified across the entire length of the encoding. Instead ofrepresenting 10¹⁰⁰, the encoding would now represent the digit “1”repeated 101 times: a very different value. Thus, a single bit error oncompressed data may actually more effectively mean a large number of biterrors. As a general guide, a single bit error may be magnified roughlyin proportion to the compression ratio of the technique used. Thus, ifthe compression technique results in compressing the data by two (thatis, taking half as much space), a single bit error effectively means twobit errors in the data; if the compression technique results incompressing the data by three (that is, taking one third as much space,a single bit error effectively means three bit errors in the data, andso on. (In the worst case, a single bit error in compressed data mightactually make it impossible to recover the raw data at all.)

Thus, while the entries in reliability table 405 of FIG. 4 are a usefulstarting point for the reliability of SSD 130, they may not completelyrepresent the true reliability of SSD 130. To that end, SSD 130(possibly through configuration module 340) may track transactions (ofwhich data deduplication and compression are two examples) being carriedout on behalf of applications 505-1 and 505-2, and use thosetransactions to determine a multiplier. The reliability of SSD 130 (asdetermined from reliability table 405 of FIG. 4 based on theconfiguration of SSD 130) may then be multiplied by this multiplier todetermine the effective reliability rate of SSD 130.

The multiplier for the reliability rate may be determined using anydesired approaches. For example, SSD 130 may track a particulartransaction, determine the multiplier applicable to that transaction,and then keep the larger of that multiplier and the previous multiplier.But this approach assumes that multipliers are independent of eachother. If data deduplication was the only technique used that couldintroduce a multiplier, or if compression was the only technique usedthat could introduce a multiplier, such an assumption might bereasonable. But if a file that is compressed is then subject to datadeduplication, a single bit error could be multiplied as a result ofboth space-saving regimens.

Thus, SSD 130 might track not only the highest multiplier to date, butalso the highest multiplier applicable to each space-saving schemeseparately. That way SSD 130 may consider not only whether the newmultiplier is the highest multiplier for a single scheme, but alsowhether the multiplier may cross schemes. For example, assume that SSD130 currently tracks the following: 2.0 for the highest compressionmultiplier, 5.0 for the highest data deduplication multiplier, and 5.0for the highest overall multiplier (on the assumption that no filesubject to compression has been stored on SSD 130 more than twice). IfSSD 130 then tracks that a file that has previously been both compressedand deduplicated is written a third time, that would mean that threecopies of that file have now been stored on SSD 130 (and deduplicated).Thus, while the this transaction does not increase either the highestcompression multiplier (since no new compression has occurred) or thehighest deduplication multiplier (since the current maximum number ofduplicates for any file is five), the highest overall multiplier may beincreased to 6.0 (as there are three copies of a compressed file subjectto 2.0 multiplier). Thus, whatever the reliability rate might otherwisebe (as may be advertised in reliability table 405 of FIG. 4 ), thatreliability rate may be multiplied by 6.0 to determine the effectivereliability for SSD 130. Alternatively, SSD 130 might track the highestmultipliers for compression and data deduplication respectively andapply both of them to a reliability to determine a minimum effectivereliability for SSD 130. (This calculation may over-emphasize the impactof transactions, since there might be no data stored on SSD 130 that issubject to both compression and data deduplication, but a conservativecalculation may nonetheless be used.)

This impact of transactions on the effective reliability of SSD 130 mayalso factor into the selection of a configuration for SSD 130. Forexample, knowing that due to data stored on SSD 130 there is amultiplier, configuration module 340 may use that multiplier whencomparing the reliability of various configurations with desiredreliabilities 510-1 and 520-2 of applications 505-1 and 505-2. That is,it may not be enough to simply compare the reliabilities listed inreliability table 405 of FIG. 4 with desired reliabilities 510-1 and510-2: the reliabilities listed in reliability table 405 of FIG. 4 mayneed to be adjusted according to the multiplier to reflect the effectivereliability of SSD 130 given the data currently stored on SSD 130.

FIG. 6 shows messages exchanged between application 505-1 of FIG. 5 andSSD 130 of FIG. 1 . In one embodiment of the inventive concept,application 505-1 may send reliability message 605 to SSD 130:reliability message 605 may include desired reliability 510-1 of FIG. 5. (Although not shown in FIG. 6 , application 505-2 of FIG. 5 , alongwith any other applications that use SSD 130, may send their own desiredreliabilities as well.) Then, SSD 130 may configure itself (usingconfiguration module 340 of FIG. 3 ) to satisfy all of the provideddesired reliabilities (that is, by satisfying the most stringentreliability provided), as shown by self-configuration 610.

But in another embodiment of the inventive concept, application 505-1may send reliability request 615. Reliability request 615 may requestthe effective reliability of SSD 130 (determined as described above),which may be returned as message 620. Application 505-1 may also sendreliability table request 625, which may request reliability table 405of FIG. 4 from SSD 130: SSD 130 may respond by returning reliabilitytable 405 of FIG. 4 in message 630. Application 505-1 may then selectthe configuration that provides a sufficient reliability (desiredreliability 470 of FIG. 5 or some superior configuration), and may sendconfiguration request 635 to SSD 130, identifying the entry inreliability table 405 of FIG. 4 that application 505-1 desires. SSD 130may then configure itself according to the identified entry ofreliability table 405, as shown by self-configuration 640.

But note that self-configuration 640 is shown in dashed lines. There aretwo reasons for this. First, presumably application 505-1 would comparethe effective reliability rate received in message 620: if the effectivereliability rate is higher than desired reliability 510-1 of FIG. 5 ,then application 505-1 would not send configuration request 635 (inwhich case self-configuration 640 would not be needed). But in someembodiments of the inventive concept application 505-1 might not requestthe effective reliability from SSD 130, instead simply selecting thedesired configuration from reliability table 405 of FIG. 4 and sendingconfiguration request 635 accordingly. In such embodiments of theinventive concept, SSD 130 (perhaps via configuration module 340) maycompare the effective reliability with the configuration identified inconfiguration request 635. If the effective reliability of SSD 130 isgreater than the reliability of the configuration identified inconfiguration request 635, SSD 130 may skip self-configuration 640(since the current configuration is already good enough).

Second, as noted above, application 505-1 may not be operating inisolation: other applications (such as application 505-2 of FIG. 5 ) maybe sending their own configuration requests 635. In such a situation,SSD 130 may choose to self-configure in a manner that satisfies allapplications, and therefore may configure according to the configurationwith the highest reliability rate (on the assumption that theapplication requesting that configuration may not be satisfied by aconfiguration with a lower reliability). Thus, while SSD 130 may performself-configuration 640, self-configuration 640 may involve a differentconfiguration than that specified in configuration request 635.

In FIG. 6 , configuration module 340 may respond to application 505-1 inconfiguring SSD 130 of FIG. 1 . But configuration module 340 may alsooperate “spontaneously” to configure SSD 130 of FIG. 1 . For example,given a desired reliability (which may be desired reliability 510-1 ofFIG. 5 as received from application 505-1 in reliability message 605, orwhich may be the advertised reliability of SSD 130 of FIG. 1 , accordingto the manufacturer, among other possibilities), configuration module340 may track the effective reliability of SSD 130 of FIG. 1 . If theeffective reliability of SSD 130 of FIG. 1 should drop below the desiredreliability, configuration module 340 may select a new configurationthat provides the desired reliability (factoring in any multipliers), toensure that the reliability of SSD 130 of FIG. 1 remains at anacceptable level.

It is worth mentioning how configuration module 340 may configure SSD130 of FIG. 1 . As discussed above, the entries in reliability table 405of FIG. 4 specify particular schemes to be used by memory chips 315-1through 315-8 of FIG. 3 , ECC module 330 of FIG. 3 , and RAID/ErasureCoding module 335 of FIG. 3 . To configure SSD 130 of FIG. 1 ,configuration module 340 may instruct these components regarding whatschemes to use. That is, configuration module 340 may instruct memorychips 315-1 through 315-8 of FIG. 3 to store a particular number of bitsin each cell, and/or instruct ECC module 330 of FIG. 3 to use aparticular ECC scheme, and/or instruct RAID/Erasure Coding module 335 ofFIG. 3 to use a particular erasure coding scheme. Note that changingschemes with data already in place may involve reading data from SSD 130of FIG. 1 and changing the scheme applied to that data, so thatsufficient reliability is maintained. Thus, for example, if data iscurrently stored using four bits in each QLC cell but now needs to bestored with only two bits in each QLC cell, the data in memory chips315-1 through 315-8 of FIG. 8 may be read, buffered temporarilysomewhere (either in some local storage or in the main memory of server110), then written back to memory chips 315-1 through 315-8 using thenew storage scheme. Similarly, applying a new ECC scheme or ErasureCoding scheme may involve reading data from and writing data to SSD 130to apply the changes.

FIG. 7 shows a flowchart of an example procedure for SSD 130 of FIG. 1to configure itself to provide a desired reliability, according to anembodiment of the inventive concept. In FIG. 7 , at block 705,configuration module 340 of FIG. 3 may determine a desired reliabilityfor SSD 130 of FIG. 1 . As discussed above, configuration module 340 ofFIG. 3 may select its own desired reliability, or it may receive desiredreliability 510-1 of FIG. 5 from application 505-1 of FIG. 5 inreliability message 605 of FIG. 6 . At block 710, configuration module340 of FIG. 3 may determine the effective reliability of SSD 130 of FIG.1 . At block 715, configuration module 340 of FIG. 3 may compare theeffective reliability of SSD 130 of FIG. 1 with the desired reliability(factoring in any multipliers due to transactions). If the effectivereliability is enough to satisfy the desired reliability, thenprocessing is complete, and configuration module 340 of FIG. 3 need donothing further.

On the other hand, if effective reliability is less than the desiredreliability, then at block 720, configuration module 340 of FIG. 3 mayaccess reliability table 405 of FIG. 4 to consider entries therein. Atblock 725, configuration module 340 of FIG. 3 may select an entry inreliability table 405 of FIG. 4 that has a reliability at least as high(factoring in any multipliers) as the desired reliability. At block 730,configuration module 340 of FIG. 3 may configure SSD 130 of FIG. 1according to the configuration in the selected entry in reliabilitytable 405 of FIG. 4 , after which processing is complete.

FIG. 8 shows a flowchart of an example procedure for SSD 130 of FIG. 1to configure itself. In FIG. 8 , at block 805, configuration module 340of FIG. 3 may configure one or more memory chips 315-1 through 315-8 ofFIG. 3 to use a particular storage scheme. At block 810, configurationmodule 340 of FIG. 3 may configure ECC module 330 of FIG. 3 to use aparticular error correcting code scheme. At block 815, configurationmodule 340 of FIG. 3 may configure RAID/Erasure Coding module 335 ofFIG. 3 to use a particular Erasure Coding scheme. Blocks 805, 810, and815 are all individually optional and may be omitted, as shown by dashedlines 820, 825, and 830.

FIGS. 9A-9B show a flowchart of an example procedure for SSD 130 of FIG.1 to determine a desired reliability. In FIG. 9A, at block 905, SSD 130of FIG. 1 may receive reliability message 605 of FIG. 6 , which mayspecify the desired reliability of SSD 130.

Alternatively, at block 910 (FIG. 9B), SSD 130 of FIG. 1 may receivereliability request 615 of FIG. 6 from application 505-1 of FIG. 5 . Atblock 915, SSD 130 of FIG. 1 may determine the effective reliability ofSSD 130 of FIG. 1 . At block 920, SSD 130 may send the effectivereliability to application 505-1 of FIG. 5 as message 620 of FIG. 6 .Note that blocks 910, 915, and 920 are optional, as shown by dashed line925.

At block 930, application 505-1 of FIG. 5 may send reliability tablerequest 625 of FIG. 6 . At block 935, SSD 130 of FIG. 1 may retrievereliability table 405 of FIG. 4 from reliability table storage 345 ofFIG. 3 . At block 940, SSD 130 of FIG. 1 may send reliability table 405of FIG. 4 to application 505-1 of FIG. 5 as message 630. Finally, atblock 945, application 505-1 of FIG. 5 may send configuration request635 to SSD 130 of FIG. 1 , requesting that configuration module 340 ofFIG. 3 configure SSD 130 of FIG. 1 according to an entry in reliabilitytable 405 identified in configuration request 635 of FIG. 6 .

FIG. 10 shows a flowchart of an example procedure for SSD 130 of FIG. 1to determine the effective reliability of SSD 130 of FIG. 1 . In FIG. 10, at block 1005, SSD 130 of FIG. 1 may determine the advertisedreliability of SSD 130 of FIG. 1 (at least, according to the currentconfiguration of SSD 130 of FIG. 1 ). At block 1010, SSD 130 may track acurrent transaction requested by (or on behalf of) application 505-1 ofFIG. 5 . At block 1015, SSD 130 of FIG. 1 may determine a multiplier (ormore than one multiplier) responsive to the current transactions (andprevious transactions). Finally, at block 1020, SSD 130 of FIG. 1 maymultiply the advertised reliability by the multiplier/multipliers todetermine the effective reliability of SSD 130 of FIG. 1 .

FIGS. 11A-11B show a flowchart of an example procedure for application505-1 of FIG. 5 to instruct SSD 130 of FIG. 1 to provide a desiredreliability, according to an embodiment of the inventive concept. InFIG. 11A, at block 1105, application 505-1 of FIG. 5 may simply senddesired reliability 510-1 of FIG. 5 to SSD 130 of FIG. 1 (as reliabilitymessage 605 of FIG. 6 ). At this point, application 505-1 of FIG. 5 maybe done, leaving it to SSD 130 of FIG. 1 to ensure desired reliability510-1 of FIG. 5 is provided.

Alternatively, at block 1110, application 505-1 of FIG. 5 may sendreliability request 615 of FIG. 6 to SSD 130 of FIG. 1 . At block 1115,application 505-1 of FIG. 5 may receive the current effectivereliability of SSD 130 of FIG. 1 in message 620 of FIG. 6 . At block1120, application 505-1 of FIG. 5 may compare the effective reliabilityof SSD 130 of FIG. 1 (as received in message 620 of FIG. 6 ) withdesired reliability 510-1 of FIG. 5 . If the effective reliability ofSSD 130 of FIG. 1 is at least as high as desired reliability 510-1 ofFIG. 5 , then processing may end (as nothing need be done).

On the other hand, if the effective reliability of SSD 130 of FIG. 1 isless than desired reliability 510-1 of FIG. 5 (or if application 505-1of FIG. 5 opts to request that SSD 130 of FIG. 1 be configured with aparticular configuration regardless of its effective reliability, asshown by dashed arrow 1125), then at block 1130 (FIG. 11B), application505-1 of FIG. 5 may send reliability table request 625 of FIG. 6 to SSD130 of FIG. 1 . At block 1135, SSD 130 of FIG. 1 may send reliabilitytable 405 of FIG. 4 to application 505-1 of FIG. 5 as message 630. Atblock 1140, application 505-1 of FIG. 5 may select an entry inreliability table 405 of FIG. 4 that provides the desired reliability.Finally, at block 1145, application 505-1 of FIG. 5 may sendconfiguration request 635 of FIG. 6 , requesting that SSD 130 of FIG. 1be configured according to the selected entry in reliability table 405of FIG. 4 .

In FIGS. 7-11B, some embodiments of the inventive concept are shown. Buta person skilled in the art will recognize that other embodiments of theinventive concept are also possible, by changing the order of theblocks, by omitting blocks, or by including links not shown in thedrawings. All such variations of the flowcharts are considered to beembodiments of the inventive concept, whether expressly described ornot.

Embodiments of the inventive concept offer technical advantages over theprior art. In conventional systems, the reliability of a storage deviceis set by the manufacturer and is basically outside the control of theuser. Embodiments of the inventive concept not only give the customersome level of control over the reliability of the storage device buteven permit automating such management. Applications may specify thedesired reliability (or may specify a particular configuration of thestorage device that implements a desired reliability). The storagedevice may then maintain that degree of reliability by changing theconfiguration as needed based on usage of the storage device.

The following discussion is intended to provide a brief, generaldescription of a suitable machine or machines in which certain aspectsof the inventive concept may be implemented. The machine or machines maybe controlled, at least in part, by input from conventional inputdevices, such as keyboards, mice, etc., as well as by directivesreceived from another machine, interaction with a virtual reality (VR)environment, biometric feedback, or other input signal. As used herein,the term “machine” is intended to broadly encompass a single machine, avirtual machine, or a system of communicatively coupled machines,virtual machines, or devices operating together. Exemplary machinesinclude computing devices such as personal computers, workstations,servers, portable computers, handheld devices, telephones, tablets,etc., as well as transportation devices, such as private or publictransportation, e.g., automobiles, trains, cabs, etc.

The machine or machines may include embedded controllers, such asprogrammable or non-programmable logic devices or arrays, ApplicationSpecific Integrated Circuits (ASICs), embedded computers, smart cards,and the like. The machine or machines may utilize one or moreconnections to one or more remote machines, such as through a networkinterface, modem, or other communicative coupling. Machines may beinterconnected by way of a physical and/or logical network, such as anintranet, the Internet, local area networks, wide area networks, etc.One skilled in the art will appreciate that network communication mayutilize various wired and/or wireless short range or long range carriersand protocols, including radio frequency (RF), satellite, microwave,Institute of Electrical and Electronics Engineers (IEEE) 802.11,Bluetooth®, optical, infrared, cable, laser, etc.

Embodiments of the present inventive concept may be described byreference to or in conjunction with associated data including functions,procedures, data structures, application programs, etc. which whenaccessed by a machine results in the machine performing tasks ordefining abstract data types or low-level hardware contexts. Associateddata may be stored in, for example, the volatile and/or non-volatilememory, e.g., RAM, ROM, etc., or in other storage devices and theirassociated storage media, including hard-drives, floppy-disks, opticalstorage, tapes, flash memory, memory sticks, digital video disks,biological storage, etc. Associated data may be delivered overtransmission environments, including the physical and/or logicalnetwork, in the form of packets, serial data, parallel data, propagatedsignals, etc., and may be used in a compressed or encrypted format.Associated data may be used in a distributed environment, and storedlocally and/or remotely for machine access.

Embodiments of the inventive concept may include a tangible,non-transitory machine-readable medium comprising instructionsexecutable by one or more processors, the instructions comprisinginstructions to perform the elements of the inventive concepts asdescribed herein.

The various operations of methods described above may be performed byany suitable means capable of performing the operations, such as varioushardware and/or software component(s), circuits, and/or module(s). Thesoftware may comprise an ordered listing of executable instructions forimplementing logical functions, and may be embodied in any“processor-readable medium” for use by or in connection with aninstruction execution system, apparatus, or device, such as a single ormultiple-core processor or processor-containing system.

The blocks or steps of a method or algorithm and functions described inconnection with the embodiments disclosed herein may be embodieddirectly in hardware, in a software module executed by a processor, orin a combination of the two. If implemented in software, the functionsmay be stored on or transmitted over as one or more instructions or codeon a tangible, non-transitory computer-readable medium. A softwaremodule may reside in Random Access Memory (RAM), flash memory, Read OnlyMemory (ROM), Electrically Programmable ROM (EPROM), ElectricallyErasable Programmable ROM (EEPROM), registers, hard disk, a removabledisk, a CD ROM, or any other form of storage medium known in the art.

Having described and illustrated the principles of the inventive conceptwith reference to illustrated embodiments, it will be recognized thatthe illustrated embodiments may be modified in arrangement and detailwithout departing from such principles, and may be combined in anydesired manner. And, although the foregoing discussion has focused onparticular embodiments, other configurations are contemplated. Inparticular, even though expressions such as “according to an embodimentof the inventive concept” or the like are used herein, these phrases aremeant to generally reference embodiment possibilities, and are notintended to limit the inventive concept to particular embodimentconfigurations. As used herein, these terms may reference the same ordifferent embodiments that are combinable into other embodiments.

The foregoing illustrative embodiments are not to be construed aslimiting the inventive concept thereof. Although a few embodiments havebeen described, those skilled in the art will readily appreciate thatmany modifications are possible to those embodiments without materiallydeparting from the novel teachings and advantages of the presentdisclosure. Accordingly, all such modifications are intended to beincluded within the scope of this inventive concept as defined in theclaims.

Embodiments of the inventive concept may extend to the followingstatements, without limitation:

Statement 1. An embodiment of the inventive concept includes a SolidState Drive (SSD), comprising:

an interface to receive read requests and write requests from a firstapplication on a host;

storage for data, the storage including at least one chip;

an SSD controller to process the read requests and the write requestsfrom the first application on the host using the storage;

a configuration module to configure the SSD; and

storage for a reliability table, the reliability table including atleast a first entry and a second entry, the first entry identifying afirst configuration of the SSD and a first reliability for the firstconfiguration of the SSD, and the second entry identifying a secondconfiguration of the SSD and a second reliability for the secondconfiguration of the SSD.

Statement 2. An embodiment of the inventive concept includes the SSDaccording to statement 1, wherein the interface may receive aconfiguration request from the first application on the host.

Statement 3. An embodiment of the inventive concept includes the SSDaccording to statement 2, wherein the configuration request includes anidentifier of one of the first entry and the second entry in thereliability table.

Statement 4. An embodiment of the inventive concept includes the SSDaccording to statement 3, wherein the configuration module mayreconfigure the SSD according to the identifier of one of the firstentry and the second entry in the reliability table.

Statement 5. An embodiment of the inventive concept includes the SSDaccording to statement 1, wherein the interface may receive areliability message from the first application on the host, thereliability message including a first desired reliability for the firstapplication on the host.

Statement 6. An embodiment of the inventive concept includes the SSDaccording to statement 5, wherein the configuration module may configurethe SSD according to one of the first entry and the second entry in thereliability table based on at least the first desired reliability.

Statement 7. An embodiment of the inventive concept includes the SSDaccording to statement 6, wherein the configuration module may configurethe SSD according to one of the first entry and the second entry in thereliability table based on at least the first desired reliability forthe first application on the host and a second desired reliability for asecond application on the host.

Statement 8. An embodiment of the inventive concept includes the SSDaccording to statement 1, wherein the at least one chip offers at leasta first storage scheme with a first chip reliability and a secondstorage scheme with a second chip reliability.

Statement 9. An embodiment of the inventive concept includes the SSDaccording to statement 8, wherein the first configuration of the SSDidentifies the first storage scheme and the second configuration of theSSD identifies the second storage scheme.

Statement 10. An embodiment of the inventive concept includes the SSDaccording to statement 1, further comprising an Error Correcting Code(ECC) module, the ECC module offering at least a first ECC scheme with afirst ECC reliability and a second ECC scheme with a second ECCreliability.

Statement 11. An embodiment of the inventive concept includes the SSDaccording to statement 10, wherein the first configuration of the SSDidentifies the first ECC scheme and the second configuration of the SSDidentifies the second ECC scheme.

Statement 12. An embodiment of the inventive concept includes the SSDaccording to statement 1, further comprising at least one of an ErasureCoding module or a Redundant Array of Independent Disks (RAID) module,the Erasure Coding module offering at least a first Erasure Codingscheme with a first Erasure Coding reliability and a second ErasureCoding scheme with a second Erasure Coding reliability and the RAIDmodule offering at least a first RAID scheme with a first RAIDreliability and a second RAID scheme with a second RAID reliability.

Statement 13. An embodiment of the inventive concept includes the SSDaccording to statement 12, wherein the first configuration of the SSDidentifies at least one of the first Erasure Coding scheme or the firstRAID scheme and the second configuration of the SSD identifies at leastone of the second Erasure Coding scheme or the second RAID scheme.

Statement 14. An embodiment of the inventive concept includes the SSDaccording to statement 1, wherein the first entry in the reliabilitytable identifies at least one of a first space overhead or a firstperformance for the first configuration of the SSD, and the second entryin the reliability table identifies at least one of a second spaceoverhead or a second performance for the second configuration of theSSD.

Statement 15. An embodiment of the inventive concept includes the SSDaccording to statement 1, wherein the at least one chip includes atleast one NAND flash chip.

Statement 16. An embodiment of the inventive concept includes a method,comprising:

determining a desired reliability for a Solid State Drive (SSD), the SSDincluding storage for data, the storage including at least one chip;

accessing a first entry in a reliability table from the SSD, thereliability table including at least the first entry and a second entry,the first entry identifying a first configuration of the SSD and a firstreliability for the first configuration of the SSD, and the second entryidentifying a second configuration of the SSD and a second reliabilityfor the second configuration of the SSD; and

configuring the SSD according to the first entry.

Statement 17. An embodiment of the inventive concept includes the methodaccording to statement 16, wherein:

the first entry includes a first storage scheme for the chip;

the second entry includes a second storage scheme for the chip; and

configuring the SSD according to the first entry includes configuringthe chip according to the first storage scheme or the second storagescheme.

Statement 18. An embodiment of the inventive concept includes the methodaccording to statement 16, wherein:

the SSD includes an Error Correcting Code (ECC) module;

the first entry includes a first ECC scheme for the ECC module;

the second entry includes a second storage scheme for the ECC module;and

configuring the SSD according to the first entry includes configuringthe ECC module according to the first ECC scheme or the second ECCscheme.

Statement 19. An embodiment of the inventive concept includes the methodaccording to statement 16, wherein:

the SSD includes at least one of an Erasure Coding module or a RedundantArray of Independent Disks (RAID) module;

the first entry includes at least one of a first Erasure Coding schemefor the Erasure Coding module or a first RAID scheme for the RAIDmodule;

the second entry includes at least one of a second Erasure Coding schemefor the Erasure Coding module or a second RAID scheme for the RAIDmodule; and

configuring the SSD according to the first entry includes configuringthe at least one of the Erasure Coding module according to the firstErasure Coding scheme or the second Erasure Coding scheme or the RAIDmodule according to the first RAID scheme or the second RAID scheme.

Statement 20. An embodiment of the inventive concept includes the methodaccording to statement 16, wherein determining a desired reliability fora Solid State Drive (SSD) includes receiving the desired reliability atthe SSD from an application on a host.

Statement 21. An embodiment of the inventive concept includes the methodaccording to statement 20, wherein accessing a first entry in areliability table from the SSD includes:

accessing the first entry and the second entry in the reliability table;and

identifying that the first entry includes a reliability at least as highas the desired reliability.

Statement 22. An embodiment of the inventive concept includes the methodaccording to statement 16, further comprising:

receiving from the application on the host at the SSD a reliabilityrequest for an effective reliability for the SSD;

determining the effective reliability for the SSD; and

sending the effective reliability from the SSD to the application on thehost.

Statement 23. An embodiment of the inventive concept includes the methodaccording to statement 22, wherein determining the effective reliabilityfor the SSD includes:

determining an advertised reliability for the SSD;

tracking an operation on the SSD;

determining a multiplier based on the operation on the SSD; and

multiplying the advertised reliability by the multiplier to determinethe effective reliability.

Statement 24. An embodiment of the inventive concept includes the methodaccording to statement 16, wherein accessing a first entry in areliability table from the SSD includes receiving an identifier of thefirst entry in the reliability table from the application on the host atthe SSD.

Statement 25. An embodiment of the inventive concept includes the methodaccording to statement 24, wherein sending the effective reliabilityfrom the SSD to the application on the host includes sending the firstentry and the second entry in the reliability table to the applicationon the host from the SSD.

Statement 26. An embodiment of the inventive concept includes the methodaccording to statement 16, wherein:

the first entry in the reliability table identifies at least one of afirst space overhead or a first performance for the first configurationof the SSD;

the second entry in the reliability table identifies at least one of asecond space overhead or a second performance for the secondconfiguration of the SSD; and

accessing a first entry in a reliability table from the SSD includesaccessing the first entry in the reliability table from the SSD based onat least the desired reliability and at least one of a desired spaceoverhead or a desired performance.

Statement 27. An embodiment of the inventive concept includes the methodaccording to statement 16, wherein the at least one chip includes atleast one NAND flash chip.

Statement 28. An embodiment of the inventive concept includes a method,comprising:

sending a reliability request from an application on a host to an SSD,the reliability request requesting an effective reliability for the SSD;

receiving the effective reliability for the SSD from the SSD at theapplication on the host;

sending a reliability table request from the application on the host tothe SSD, the reliability table request requesting a reliability tablestored on the SSD;

receiving the reliability table from the SSD at the application on thehost, each entry in the reliability table identifying a configuration ofthe SSD and a reliability for the configuration of the SSD;

selecting an entry in the reliability table based on at least a desiredreliability for the application on the host; and

sending a configuration request to the SSD from the application on thehost, the configuration request identifying the entry in the reliabilitytable.

Statement 29. An embodiment of the inventive concept includes the methodaccording to statement 28, further comprising:

comparing the effective reliability for the SSD with a desiredreliability for the application on the host; and

based on at least the effective reliability for the SSD exceeding thedesired reliability for the application on the host, not sending theconfiguration request to the SSD.

Statement 30. An embodiment of the inventive concept includes the methodaccording to statement 28, wherein selecting an entry in the reliabilitytable based on at least a desired reliability for the application on thehost includes selecting the entry in the reliability table for which thereliability for the configuration of the SSD is at least as high as thedesired reliability.

Statement 31. An embodiment of the inventive concept includes the methodaccording to statement 28, wherein:

each entry in the reliability table further identifies at least one of afirst space overhead or a first performance for the configuration of theSSD;

the second entry in the reliability table identifies at least one of asecond space overhead or a second performance; and

selecting an entry in the reliability table based on at least a desiredreliability for the application on the host includes selecting the entryin the reliability table based on at least the desired reliability forthe application on the host and at least one of a desired space overheador a desired performance.

Statement 32. An embodiment of the inventive concept includes anarticle, comprising a non-transitory storage medium, the non-transitorystorage medium having stored thereon instructions that, when executed bya machine, result in:

determining a desired reliability for a Solid State Drive (SSD), the SSDincluding storage for data, the storage including at least one chip;

accessing a first entry in a reliability table from the SSD, thereliability table including at least the first entry and a second entry,the first entry identifying a first configuration of the SSD and a firstreliability for the first configuration of the SSD, and the second entryidentifying a second configuration of the SSD and a second reliabilityfor the second configuration of the SSD; and

configuring the SSD according to the first entry.

Statement 33. An embodiment of the inventive concept includes thearticle according to statement 32, wherein:

the first entry includes a first storage scheme for the chip;

the second entry includes a second storage scheme for the chip; and

configuring the SSD according to the first entry includes configuringthe chip according to the first storage scheme or the second storagescheme.

Statement 34. An embodiment of the inventive concept includes thearticle according to statement 32, wherein:

the SSD includes an Error Correcting Code (ECC) module;

the first entry includes a first ECC scheme for the ECC module;

the second entry includes a second storage scheme for the ECC module;and

configuring the SSD according to the first entry includes configuringthe ECC module according to the first ECC scheme or the second ECCscheme.

Statement 35. An embodiment of the inventive concept includes thearticle according to statement 32, wherein:

the SSD includes at least one of an Erasure Coding module or a RedundantArray of Independent Disks (RAID) module;

the first entry includes at least one of a first Erasure Coding schemefor the Erasure Coding module or a first RAID scheme for the RAIDmodule;

the second entry includes at least one of a second Erasure Coding schemefor the Erasure Coding module or a second RAID scheme for the RAIDmodule; and

configuring the SSD according to the first entry includes configuringthe at least one of the Erasure Coding module according to the firstErasure Coding scheme or the second Erasure Coding scheme or the RAIDmodule according to the first RAID scheme or the second RAID scheme.

Statement 36. An embodiment of the inventive concept includes thearticle according to statement 32, wherein determining a desiredreliability for a Solid State Drive (SSD) includes receiving the desiredreliability at the SSD from an application on a host.

Statement 37. An embodiment of the inventive concept includes thearticle according to statement 36, wherein accessing a first entry in areliability table from the SSD includes:

accessing the first entry and the second entry in the reliability table;and

identifying that the first entry includes a reliability at least as highas the desired reliability.

Statement 38. An embodiment of the inventive concept includes thearticle according to statement 32, the non-transitory storage mediumhaving stored thereon further instructions that, when executed by themachine, result in:

receiving from the application on the host at the SSD a reliabilityrequest for an effective reliability for the SSD;

determining the effective reliability for the SSD; and

sending the effective reliability from the SSD to the application on thehost.

Statement 39. An embodiment of the inventive concept includes thearticle according to statement 38, wherein determining the effectivereliability for the SSD includes:

determining an advertised reliability for the SSD;

tracking an operation on the SSD;

determining a multiplier based on the operation on the SSD; and

multiplying the advertised reliability by the multiplier to determinethe effective reliability.

Statement 40. An embodiment of the inventive concept includes thearticle according to statement 38, wherein accessing a first entry in areliability table from the SSD includes receiving an identifier of thefirst entry in the reliability table from the application on the host atthe SSD.

Statement 41. An embodiment of the inventive concept includes thearticle according to statement 40, wherein sending the effectivereliability from the SSD to the application on the host includes sendingthe first entry and the second entry in the reliability table to theapplication on the host from the SSD.

Statement 42. An embodiment of the inventive concept includes thearticle according to statement 32, wherein:

the first entry in the reliability table identifies at least one of afirst space overhead or a first performance for the first configurationof the SSD;

the second entry in the reliability table identifies at least one of asecond space overhead or a second performance for the secondconfiguration of the SSD; and

accessing a first entry in a reliability table from the SSD includesaccessing the first entry in the reliability table from the SSD based onat least the desired reliability and at least one of a desired spaceoverhead or a desired performance.

Statement 43. An embodiment of the inventive concept includes thearticle according to statement 32, wherein the at least one chipincludes at least one NAND flash chip.

Statement 44. An embodiment of the inventive concept includes anarticle, comprising:

sending a reliability request from an application on a host to an SSD,the reliability request requesting an effective reliability for the SSD;

receiving the effective reliability for the SSD from the SSD at theapplication on the host;

sending a reliability table request from the application on the host tothe SSD, the reliability table request requesting a reliability tablestored on the SSD;

receiving the reliability table from the SSD at the application on thehost, each entry in the reliability table identifying a configuration ofthe SSD and a reliability for the configuration of the SSD;

selecting an entry in the reliability table based on at least a desiredreliability for the application on the host; and

sending a configuration request to the SSD from the application on thehost, the configuration request identifying the entry in the reliabilitytable.

Statement 45. An embodiment of the inventive concept includes thearticle according to statement 44, the non-transitory storage mediumhaving stored thereon further instructions that, when executed by themachine, result in:

comparing the effective reliability for the SSD with a desiredreliability for the application on the host; and

based on at least the effective reliability for the SSD exceeding thedesired reliability for the application on the host, not sending theconfiguration request to the SSD.

Statement 46. An embodiment of the inventive concept includes thearticle according to statement 44, wherein selecting an entry in thereliability table based on at least a desired reliability for theapplication on the host includes selecting the entry in the reliabilitytable for which the reliability for the configuration of the SSD is atleast as high as the desired reliability.

Statement 47. An embodiment of the inventive concept includes thearticle according to statement 44, wherein:

each entry in the reliability table further identifies at least one of afirst space overhead or a first performance for the configuration of theSSD;

the second entry in the reliability table identifies at least one of asecond space overhead or a second performance; and

selecting an entry in the reliability table based on at least a desiredreliability for the application on the host includes selecting the entryin the reliability table based on at least the desired reliability forthe application on the host and at least one of a desired space overheador a desired performance.

Consequently, in view of the wide variety of permutations to theembodiments described herein, this detailed description and accompanyingmaterial is intended to be illustrative only, and should not be taken aslimiting the scope of the inventive concept. What is claimed as theinventive concept, therefore, is all such modifications as may comewithin the scope and spirit of the following claims and equivalentsthereto.

What is claimed is:
 1. A storage device, comprising: an interface toreceive a request from a first application on a host; a first storagefor data; a controller to process the request from the first applicationon the host using the storage; a configuration module to configure thestorage device; and a second storage for a data structure, the datastructure including at least a first entry and a second entry, the firstentry identifying a first configuration of the storage device and afirst performance parameter for the first configuration of the storagedevice, and the second entry identifying a second configuration of thestorage device and a second performance parameter for the secondconfiguration of the storage device.
 2. The storage device according toclaim 1, wherein: the first performance parameter includes a firstreliability; and the second performance parameter includes a secondreliability.
 3. The storage device according to claim 2, wherein theinterface may receive a configuration request from the first applicationon the host.
 4. The storage device according to claim 3, wherein theconfiguration request includes an identifier of one of the first entryand the second entry in the data structure.
 5. The storage deviceaccording to claim 2, wherein the interface may receive a reliabilitymessage from the first application on the host, the reliability messageincluding a third reliability for the first application on the host. 6.The storage device according to claim 5, wherein the configurationmodule may configure the storage device according to one of the firstentry and the second entry in the data structure based on at least thethird reliability.
 7. The storage device according to claim 2, whereinthe at least one storage offers at least a first storage scheme with athird reliability and a second storage scheme with a fourth reliability.8. The storage device according to claim 7, wherein the firstconfiguration of the storage device identifies the first storage schemeand the second configuration of the storage device identifies the secondstorage scheme.
 9. The storage device according to claim 2, furthercomprising an Error Correcting Code (ECC) module, the ECC moduleoffering at least a first ECC scheme with a third reliability and asecond ECC scheme with a fourth reliability.
 10. The storage deviceaccording to claim 9, wherein the first configuration of the storagedevice identifies the first ECC scheme and the second configuration ofthe storage device identifies the second ECC scheme.
 11. The storagedevice according to claim 2, further comprising at least one of anErasure Coding module or a RAID module, the Erasure Coding moduleoffering at least a first Erasure Coding scheme with a third reliabilityor a second Erasure Coding scheme with a fourth reliability and the RAIDmodule offering at least a first RAID scheme with a fifth reliability ora second RAID scheme with a sixth reliability.
 12. The storage deviceaccording to claim 11, wherein the first configuration of the storagedevice identifies at least one of the first Erasure Coding scheme or thefirst RAID scheme and the second configuration of the storage deviceidentifies at least one of the second Erasure Coding scheme or thesecond RAID scheme.
 13. A method, comprising: determining a firstperformance parameter for a storage device, the storage device includingstorage for data, the storage device including a second performanceparameter; accessing a first entry in a data structure from the storagedevice, the data structure including at least the first entry and asecond entry, the first entry identifying a first configuration of thestorage device and a third performance parameter for the firstconfiguration of the storage device, and the second entry identifying asecond configuration of the storage device and a fourth performanceparameter for the second configuration of the storage device, the thirdperformance parameter satisfying the first performance parameter; andconfiguring the storage device according to the first entry, wherein thefirst performance parameter is greater than the second performanceparameter for the storage device.
 14. The method according to claim 13,wherein: the first performance parameter includes a first reliability;the second performance parameter includes a second reliability; thethird performance parameter includes a third reliability; and the fourthperformance parameter includes a fourth reliability.
 15. The methodaccording to claim 14, wherein: the first entry includes a first storagescheme for the storage; the second entry includes a second storagescheme for the storage; and configuring the storage device according tothe first entry includes configuring the storage according to the firststorage scheme or the second storage scheme.
 16. The method according toclaim 14, wherein: the storage device includes an Error Correcting Code(ECC) module; the first entry includes a first ECC scheme for the ECCmodule; the second entry includes a second storage scheme for the ECCmodule; and configuring the storage device according to the first entryincludes configuring the ECC module according to the first ECC scheme orthe second ECC scheme.
 17. The method according to claim 14, wherein:the storage device includes at least one of an Erasure Coding module ora RAID module; the first entry includes at least one of a first ErasureCoding scheme for the Erasure Coding module or a first RAID scheme forthe RAID module; the second entry includes at least one of a secondErasure Coding scheme for the Erasure Coding module or a second RAIDscheme for the RAID module; and configuring the storage device accordingto the first entry includes configuring the at least one of the ErasureCoding module according to the first Erasure Coding scheme or the secondErasure Coding scheme or the RAID module according to the first RAIDscheme or the second RAID scheme.
 18. The method according to claim 14,wherein determining a first reliability for a storage device includesreceiving the first reliability at the storage device from anapplication on a host.
 19. The method according to claim 18, whereinaccessing the first entry in the data structure from the storage deviceincludes: accessing the first entry and the second entry in the datastructure; and identifying that the first entry the third reliability isat least as high as the first reliability.
 20. The method according toclaim 14, wherein accessing the first entry in the data structure fromthe storage device includes receiving an identifier of the first entryin the data structure from the application on the host at the storagedevice.
 21. A method, comprising: sending a request from an applicationon a host to a storage device, the request requesting a firstperformance parameter for the storage device; receiving the firstperformance parameter for the storage device from the storage device atthe application on the host; selecting an entry in a data structurebased on at least a second performance parameter for the application onthe host; and sending a configuration request to the storage device fromthe application on the host, the configuration request identifying theentry in the data structure.
 22. The method according to claim 21,wherein: the first performance parameter includes a first reliability;and the second performance parameter includes a second reliability. 23.The method according to claim 22, wherein selecting the entry in thedata structure based on at least the second reliability for theapplication on the host includes selecting the entry in the datastructure for which a third reliability for the configuration of thestorage device is at least as high as the second reliability.